This invention generally relates to an air return bulkhead used in temperature controlled trailers to maintain the desired flow of temperature controlled air through the trailer conditioned space; and more particularly the invention relates to a bulkhead that is easily installed in the trailer and prevents short cycling of the temperature controlled air in the conditioned space.
Temperature control units for use in trailers are mounted on a trailer which defines a conditioned space, and the air in the conditioned space is maintained at a predetermined desired temperature by the temperature control unit which is typically mounted on the front trailer wall or panel. The temperature control unit evaporator extends through the front trailer wall and into the conditioned space. A load of palletized cargo is loaded into the conditioned space and the evaporator serves to cool and force the conditioned air into the conditioned space and around the palletized load in the manner generally indicated by arrows 150 in FIG. 1. The conditioned air is forced rearwardly out the evaporator, around the back of the load and below the load and back to the front of the trailer.
An air return bulkhead is located at the front of the trailer and is typically attached to the interior of the front trailer wall and behind the temperature control unit. Prior art bulkheads have inlet openings which permit the air to pass behind the bulkhead and directly into the evaporator. The return air passes through the evaporator and the majority of the discharged volume of conditioned air returns to the conditioned space. However a portion of the conditioned air does not flow to the back of the trailer but rather "short cycles". Rather than flowing rearwardly and around the load, the short cycling air remains at the front of the load and simply returns to the evaporator through the bulkhead inlet openings. The short cycling conditioned air can negatively affect the temperature of the conditioned air.
It is well known to one skilled in the relevant art that short cycling is not desirable when frozen loads are in the conditioned space. However, a small volume of short cycled air is desirable for fresh loads such as lettuce. Therefore, it would be desirable to provide a means for easily selectably changing between permitting and preventing short cycling in bulkheads.
The foregoing illustrates limitations known to exist in present air return bulkheads. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.